Method and apparatus for coverage enhancement

Abstract

The present invention is method and apparatus for coverage enhancement. An embodiment of the present invention includes detecting a cell with primary synchronization signal (PSS) and/or secondary synchronization signal (SSS), detecting reference signal based on the detected synchronization signal, detecting broadcasting channel based on the detected reference signal and decoding master information block on the broadcasting channel, detecting system information block on a downlink data channel, transmitting random access preamble on random access channel based on a system information obtained from the system information block and receiving random access response corresponding to the random access preamble.

The invention claimed is: 
     
       1. A method of initial accessing by an user equipment (UE), the method comprising:
 detecting a cell with primary synchronization signal (PSS) and/or secondary synchronization signal (SSS); 
 detecting reference signal based on the detected synchronization signal; 
 detecting broadcasting channel based on the detected reference signal and decoding master information block on the broadcasting channel; 
 detecting system information block on a downlink data channel; and 
 transmitting random access preamble on random access channel based on a system information obtained from the system information block, wherein whether coverage enhancement is needed or not is determined based on at least one of the detected signals and system information, and 
 wherein coverage for the UE is enhanced when the coverage enhancement is determined as needed. 
 
     
     
       2. The method of  claim 1 , wherein in the step of detecting the cell, the coverage enhancement is determined as needed when the number of the synchronization signals is exceed predetermined number. 
     
     
       3. The method of  claim 2 , wherein whether the cell supports the coverage enhancement or not is determined according to a cell ID specified by the synchronization signal. 
     
     
       4. The method of  claim 1 , wherein in the step of detecting the cell, the coverage enhancement is determined as needed for a cell ID specified by the synchronization signal when the strength of the synchronization signals is lower than predetermined threshold. 
     
     
       5. The method of  claim 1 , wherein in the step of detecting the cell, whether the cell supports the coverage enhancement or not is determined according to a cell ID specified by the synchronization signal. 
     
     
       6. The method of  claim 1 , wherein in the step of detecting the broadcasting channel, the coverage enhancement is determined as needed when the broadcasting channel needs to be transmitted repeatedly for decoding the master information block. 
     
     
       7. The method of  claim 6 , wherein a coverage level is determined based on the number of broadcasting channels repeated transmitted, and wherein the coverage level specifies coverage of the UE to be enhanced. 
     
     
       8. The method of  claim 1 , wherein in the step of detecting system information block, the coverage enhancement is determined as needed when the downlink data channel needs to be transmitted repeatedly for decoding the system information block. 
     
     
       9. The method of  claim 8 , wherein a coverage level is determined based on the number of downlink data channels repeated transmitted, and wherein the coverage level specifies coverage of the UE to be enhanced. 
     
     
       10. The method of  claim 1 , wherein the number of repeated downlink transmission is signaled by higher layer or downlink control information (DCI) signaling when the number of repeated downlink transmission is changed for the UE for which coverage needs to be enhanced. 
     
     
       11. The method of  claim 1 , wherein the number of repeated system information block transmission is signaled by downlink data channel when the number of repeated system information block transmission is changed for the UE for which coverage needs to be enhanced. 
     
     
       12. The method of  claim 1 , wherein in the step of transmitting random access channel, transmission power is adjusted based on the number of repeated downlink transmission and threshold transmission power which is required by base station (BS), and
 wherein the threshold transmission power is determined based on the number of repeated downlink transmission. 
 
     
     
       13. A method of controlling transmission power by coverage limiting user equipment (UE), the method comprising:
 receiving cell specific reference signal; 
 estimating path loss based on the cell specific reference signal; and 
 determining transmission power based on the estimated path loss, wherein the transmission power is adjust based on the number of repeated downlink transmission and threshold transmission power which is required by base station (BS), and 
 wherein the threshold transmission power is determined based on the number of repeated downlink transmission.